Advances in nanotextile finishes an approach towards

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Advances in Nanotextile Finishes An Approach Towards Sustainability 45
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11.4 SEM Characterization The incorporation of PNCS microgel onto the cotton surface has been con fi rmed by SEM (Fig. 33 ). The WU and WRC results con fi rm that due to the thermorespon- siveness of PNIPAAm and pH-responsiveness of chitosan, the smart fabric absorbs more water at temperature below LCST ( * 32 °C) and with acidic pH (less than pK b chitosan * 6.5), while it absorbs less water when temperature is above LCST and pH is basic. Below LCST, the polymer chains, because of predomination of hydrogen bonding, are hydrophilic, whereas a phase separation occurs above the LCST due to predomination of hydrophobic interactions (Brojeswari et al. 2007 ). At acidic pH, amino groups of chitosan are protonated, and therefore PNIPAAm s negative charges (due to the polymerization procedure with APS, the PNIPAAm nanoparticles have negative charges) are neutralized by chitosan. Greater hydrophobicity than in their charged state results from the counterbalance of nanoparticles, where they are maintained hydrated and stable. 11.5 In fl uence of Nanohydrogel Finishing on Fabric Thickness The in fl uence of smart fi nishing on thickness of modi fi ed cotton fabrics has been evaluated. The samples 1 3 represent the cotton fabrics modi fi ed with 4, 6, and 8 (% owf) PNCS and proper amounts of the BTCA, SHP, and control sample in the cotton fabric without any hydrogel fi nishing on the surface (Bashari et al. 2015 ). The increase in thickness of the modi fi ed fabrics in comparison with control fabric indicates the presence of the smart nanogel system on fabric. For the thickness measured at 30 °C (below LCST of PNCS nanogel) and at around standard relative humidity of the environment, the effect of hydrogel presence on fabric thickness at Fig. 33 SEM micrographs of a cotton fabric treated with PNCS nanoparticles, and b control fabric (Bashari et al. 2015 ) 46 N. Gokarneshan et al.
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temperature below LCST is more than that measured at the temperature above LSCT. But there is no increase beyond 5 % in the thickness of fabric samples. 11.6 In fl uence of Nanohydrogel Finishing on Fabric CRA The CRA data of modi fi ed and reference fabrics in warp and weft directions have been obtained. The fi ndings reveal that all modi fi ed samples have a little larger CRA than control sample. This is due to the involvement of the hydroxyl groups of the cellulose chains in cross-linking reaction with PNCS nanogel and BTCA and consequently the decrease in cellulose chain mobility to create wrinkles (Bashari et al. 2015 ). Since crease recovery angle of modi fi ed fabrics in comparison with control does not show signi fi cant changes, it cannot be said that the modi fi ed fabrics with nanogel have anticreasing property. 11.7 In fl uence of Nanohydrogel Finishing on Fabric Yellowness Index The yellowness indices of the modi fi ed and control cotton fabrics were have been determined.
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  • Fall '19
  • N. Gokarneshan

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